JWT Decoder
Decode JWT headers and payloads for API debugging. Free online developer tool for fast browser-based work.
What is this tool?
JWT Decoder separates a token into header and payload so you can inspect claims while debugging authentication flows. Decoding helps you read a token, but it does not prove that the signature is valid.
How to use
- Paste a non-production JWT or a redacted token sample.
- Read the decoded header and payload fields, especially issuer, audience, subject and expiration.
- Verify signatures and permissions in your own trusted backend or identity provider before making decisions.
Practical example
A decoded payload is useful for checking whether a test token expired or has the expected audience.
Header: { "alg": "RS256", "typ": "JWT" }
Payload: { "sub": "test-user", "aud": "staging-api", "exp": 1893456000 }
Reminder: decoding is not signature verification.API
API examples should use fake or redacted tokens only. Never publish real bearer tokens in shared documentation.
When to use
Related tools
Privacy
Do not paste production tokens, session cookies, API keys or credentials. Use redacted, safe or non-production tokens for browser inspection.
Frequently asked questions
Does decoding a JWT validate it?
No. Decoding only reads header and payload. Signature validation must happen with the correct key and trusted code.
Can I paste a production token?
No. Use a staging, expired, redacted or test token so credentials are not exposed.
Which JWT fields should I check first?
Start with iss, aud, sub, exp, iat and scopes or roles, then verify the signature in your backend.
Limitations / when not to use
Do not treat decoded content as trusted. A JWT can be decoded even when its signature is missing, invalid or signed by the wrong key.